1. Field of the Invention
The present invention relates to a water-in-oil-type emulsion skin cosmetic that is excellent in stability and has non-oily usability. More specifically, the present invention relates to a water-in-oil-type emulsion skin cosmetic comprising a volatile hydrocarbon oil and a non-volatile silicone oil, which is excellent in emulsification stability.
2. Description of the Related Art
Water-in-oil-type skin cosmetics have been used as skin cosmetics for use in applications, such as sunscreen cosmetics, for which water resistance is required. However, since water-in-oil-type emulsions inevitably contain relatively a large amount of oil component, they have a problem in usability that it is felt oily when they are applied to the skin.
In order to improve the oily feeling of water-in-oil-type emulsions, a volatile oil component is incorporated. However, in some emulsions mainly comprising a volatile silicone oil as a volatile oil component, surface-slip feeling and squeaky feeling become strong and suitable moist feeling is lost after application. On the other hand, there has been a problem that, when a volatile hydrocarbon oil component is incorporated into a water-in-oil-type emulsion comprising a non-volatile silicone oil, surface-slip feeling and squeaky feeling are improved, but the stability of the emulsion over time is decreased.
Patent Document 1 describes a cosmetic composition having transfer resistance, comprising a non-volatile silicone compound and a non-volatile hydrocarbon oil component that is non-compatible with the silicone. This cosmetic comprises a volatile hydrocarbon oil component (solvent) in which a non-volatile hydrocarbon oil can be dissolved and a non-volatile silicone compound can be dissolved or dispersed, and has improved transfer resistance by specifying the solution parameter of the above-mentioned non-volatile hydrocarbon oil component.
Patent Document 2 describes a water-in-oil-type emulsion composition comprising fibers, a silicone surfactant and a clay, which is considered to have fine stability even at a high temperature (such as 45° C.).
Furthermore, Patent Document 3 describes a water-in-oil-type emulsified sunscreen cosmetic comprising a zinc oxide powder that has been subjected to a special surface-hydrophobization treatment, a volatile silicone, a polyoxyalkylene-modified organopolysiloxane and water. The literature describes that this water-in-oil-type emulsion cosmetic may further comprise an organically-modified clay mineral, and an emulsion in which the above-mentioned powder had been incorporated stably without increasing the amount of the oil component such as a non-volatile silicone was obtained.
However, the problem that the stability of a water-in-oil-type emulsion comprising a non-volatile silicone is deteriorated when a volatile hydrocarbon oil component is incorporated into the emulsion has not been recognized at all in prior arts including Patent Documents 1 to 3, and thus any solution for such problem has not been disclosed or suggested.